Silicon etching liquid and etching method

A silicon etching liquid characterized by anisotropically dissolving monocrystalline silicon therein by using an aqueous solution containing a quaternary ammonium hydroxide and an aminoguanidine salt and an etching method of silicon using the instant etching liquid are an etching liquid and an etching method enabling one to perform processing at a high etching rate in etching processing of silicon, particularly in etching processing of silicon in a manufacturing process of MEMS parts or semiconductor devices.